For some people hanging art always involves a leveling laser, a tape measure, and math; others dive in without measuring. Sister Parish was famous for not measuring.
Whichever way you like to approach it, there are some helpful guidelines that editors, art collectors, and designers seem to agree on. Domino: The Book of Decorating recommends starting with one large piece, then adding smaller works to the arrangement. The secondary pieces you add might be hung with perfect symmetry or could be quite random.
I was asked to share asymmetric examples, so here is a look at some old favorites including multiple views of Miles Redd's house, courtesy NY Social Diary. (To many of us, Redd is a genius at displaying pictures!) If you are interested in formal principles, this Southern Accents story is helpful.
Definitely in the loose, informal camp is Kathryn Ireland. She prefers an unstudied look. But as you can see below, she did stick with the classic formula: very large centered mirror flanked by smaller (and not-so-small) paintings.
Rayman Boozer seems to go by instinct, his apartment is shown below.
Caroline Clifton-Mogg says, "The role of both frame and mat is not to subdue or conflict but to flatter and complement the image they surround."
She adds that small oils can sometimes lose impact when framed according to conventional proportions, so it may be acceptable to use a wider, bolder frame. In general though, "The frame should be almost respectfully reticent in the presence of artistic merit."
Image one is Lisa Fine's apartment as seen in the November 2008 Elle Decor. Fine owns a Kara Walker, an ink drawing placed to the left of the portrait of Malula, Fine's late dog.
Images two through six are Redd's work from NY Social Diary.
Ireland's living room is from Classic Country published by Gibbs Smith, 2007.
Rayman Boozer's apartment is from the May 2006 Elle Decor.
Image ten is from domino, February 2009.
The last image is Windsor Smith, Western Interiors, October 2008, via Smith's site.
Clifton-Mogg quotes are from Displaying Pictures.